1. Field of the Invention
The present invention relates to a thermal transfer sheet, for a protective layer, with a protective layer separably provided thereon. More particularly, the present invention relates to a protective layer transfer sheet that can yield a protective layer, which can impart stampability and writability with a pen using an aqueous ink, a fountain pen or the like to an image formed by thermal transfer recording and is excellent in layer transferability, abrasion resistance, scratch resistance, weathering resistance, chemical resistance, solvent resistance and the like, and a thermally transferred image recorded object and a print using the same.
2. Background Art
At the present time, thermal transfer recording is widely used as a simple printing method. The thermal transfer recording can simply form various images and thus is utilized in printing wherein the number of prints may be relatively small, for example, in the preparation of ID cards, such as identification cards or photographs for business, or is utilized, for example, in printers of personal computers or video printers.
When a full-color gradational image such as a photograph-like image of a face is desired, the thermal transfer sheet used is such that, for example, colorant layers of yellow, magenta, and cyan and optionally black are provided as ink layers repeatedly in a large number in a face serial manner on a continuous substrate sheet.
Such thermal transfer sheets are classified roughly into thermal transfer sheets of the so-called “heat-fusion” or “thermal ink transfer” type wherein the colorant layer is melted and softened upon heating and as such is transferred onto an object, that is, an image-receiving sheet, and thermal transfer sheets of the so-called “sublimation dye transfer” or “thermal dye transfer” type wherein, upon heating, a dye contained in the colorant layer is sublimated to permit the dye to migrate onto the image-receiving sheet.
When the above thermal transfer sheet is used, for example, for preparing identification cards or documents, a method known for forming a protective layer on an mage with a view to protecting the image is that a protective layer transfer sheet with a thermally transferable resin layer is stacked on an image formed by the thermal transfer of a heat-fusion colorant layer or thermally sublimable dye and the thermally transferable resin layer is transferred by means of a thermal head, a heating roll or the like to form a protective layer on the image.
The provision of the protective layer can improve abrasion resistance, chemical resistance, solvent resistance and the like of images, and, further, the addition of an ultraviolet absorber or the like to the protective layer can improve lightfastness of the images.
For example, Japanese Patent Laid-Open No. 240404/2002 discloses a thermal transfer sheet for a protective layer in which a thermally transferable protective layer is provided on at least a part of one side of a substrate sheet and the protective layer is a laminate having a structure of at least two layers, that is, comprises at least a layer composed mainly of an acrylic resin and a layer composed mainly of a polyester resin provided in that order on the substrate sheet.
The thermal transfer sheet for a protective layer disclosed in Japanese Patent Laid-Open No. 240404/2002, however, is disadvantageous in that when the formation of aqueous ink images, for example, stamps put at the joining of two leaves, or various stamp images, using an aqueous ink on a thermally transferred image, with a protective layer formed using the thermal transfer sheet for a protective layer, on a photographic paper is contemplated for use, e.g., in a photographic image of a face in a passport, the print cannot absorb and fix the aqueous ink.
To overcome the above problem, for example, Japanese Patent Laid-Open No. 324140/1996 discloses a thermal transfer film for a protective layer. Upon transfer, the thermal transfer film for a protective layer forms a protective layer, for example, in which a water absorptive surface layer constituting the uppermost surface after transfer is a layer capable of absorbing and fixing an aqueous ink and the water absorptive surface layer is a substantially transparent porous layer or a partially water absorptive layer comprising at least water absorptive micro-regions and water resistant micro-regions.
In the thermal transfer film for a protective layer disclosed in Japanese Patent Laid-Open No. 324140/1996, however, the following facts should be noted. Specifically, when a water absorptive surface layer is provided in the transferred protective layer for water absorptive property-imparting purposes, as compared with a conventional thermal transfer sheet for a protective layer which does not impart the water absorptive property, at the time of thermal transfer, disadvantageously, the transferability of the protective layer from a substrate film is poor, that is, the protective layer is not faithfully separated.